block/bochs.c

   1 /*
   2  * Block driver for the various disk image formats used by Bochs
   3  * Currently only for "growing" type in read-only mode
   4  *
   5  * Copyright (c) 2005 Alex Beregszaszi
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25 #include "qemu/osdep.h"
  26 #include "qapi/error.h"
  27 #include "qemu-common.h"
  28 #include "block/block_int.h"
  29 #include "qemu/module.h"
  30
  31 /**************************************************************/
  32
  33 #define HEADER_MAGIC "Bochs Virtual HD Image"
  34 #define HEADER_VERSION 0x00020000
  35 #define HEADER_V1 0x00010000
  36 #define HEADER_SIZE 512
  37
  38 #define REDOLOG_TYPE "Redolog"
  39 #define GROWING_TYPE "Growing"
  40
  41 // not allocated: 0xffffffff
  42
  43 // always little-endian
  44 struct bochs_header {
  45     char magic[32];     /* "Bochs Virtual HD Image" */
  46     char type[16];      /* "Redolog" */
  47     char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
  48     uint32_t version;
  49     uint32_t header;    /* size of header */
  50
  51     uint32_t catalog;   /* num of entries */
  52     uint32_t bitmap;    /* bitmap size */
  53     uint32_t extent;    /* extent size */
  54
  55     union {
  56         struct {
  57             uint32_t reserved;  /* for ??? */
  58             uint64_t disk;      /* disk size */
  59             char padding[HEADER_SIZE - 64 - 20 - 12];
  60         } QEMU_PACKED redolog;
  61         struct {
  62             uint64_t disk;      /* disk size */
  63             char padding[HEADER_SIZE - 64 - 20 - 8];
  64         } QEMU_PACKED redolog_v1;
  65         char padding[HEADER_SIZE - 64 - 20];
  66     } extra;
  67 } QEMU_PACKED;
  68
  69 typedef struct BDRVBochsState {
  70     CoMutex lock;
  71     uint32_t *catalog_bitmap;
  72     uint32_t catalog_size;
  73
  74     uint32_t data_offset;
  75
  76     uint32_t bitmap_blocks;
  77     uint32_t extent_blocks;
  78     uint32_t extent_size;
  79 } BDRVBochsState;
  80
  81 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  82 {
  83     const struct bochs_header *bochs = (const void *)buf;
  84
  85     if (buf_size < HEADER_SIZE)
  86         return 0;
  87
  88     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
  89         !strcmp(bochs->type, REDOLOG_TYPE) &&
  90         !strcmp(bochs->subtype, GROWING_TYPE) &&
  91         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
  92         (le32_to_cpu(bochs->version) == HEADER_V1)))
  93         return 100;
  94
  95     return 0;
  96 }
  97
  98 static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
  99                       Error **errp)
 100 {
 101     BDRVBochsState *s = bs->opaque;
 102     uint32_t i;
 103     struct bochs_header bochs;
 104     int ret;
 105
 106     bs->read_only = 1; // no write support yet
 107     bs->request_alignment = BDRV_SECTOR_SIZE; /* No sub-sector I/O supported */
 108
 109     ret = bdrv_pread(bs->file->bs, 0, &bochs, sizeof(bochs));
 110     if (ret < 0) {
 111         return ret;
 112     }
 113
 114     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 115         strcmp(bochs.type, REDOLOG_TYPE) ||
 116         strcmp(bochs.subtype, GROWING_TYPE) ||
 117         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 118         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 119         error_setg(errp, "Image not in Bochs format");
 120         return -EINVAL;
 121     }
 122
 123     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 124         bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
 125     } else {
 126         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 127     }
 128
 129     /* Limit to 1M entries to avoid unbounded allocation. This is what is
 130      * needed for the largest image that bximage can create (~8 TB). */
 131     s->catalog_size = le32_to_cpu(bochs.catalog);
 132     if (s->catalog_size > 0x100000) {
 133         error_setg(errp, "Catalog size is too large");
 134         return -EFBIG;
 135     }
 136
 137     s->catalog_bitmap = g_try_new(uint32_t, s->catalog_size);
 138     if (s->catalog_size && s->catalog_bitmap == NULL) {
 139         error_setg(errp, "Could not allocate memory for catalog");
 140         return -ENOMEM;
 141     }
 142
 143     ret = bdrv_pread(bs->file->bs, le32_to_cpu(bochs.header), s->catalog_bitmap,
 144                      s->catalog_size * 4);
 145     if (ret < 0) {
 146         goto fail;
 147     }
 148
 149     for (i = 0; i < s->catalog_size; i++)
 150         le32_to_cpus(&s->catalog_bitmap[i]);
 151
 152     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 153
 154     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
 155     s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
 156
 157     s->extent_size = le32_to_cpu(bochs.extent);
 158     if (s->extent_size < BDRV_SECTOR_SIZE) {
 159         /* bximage actually never creates extents smaller than 4k */
 160         error_setg(errp, "Extent size must be at least 512");
 161         ret = -EINVAL;
 162         goto fail;
 163     } else if (!is_power_of_2(s->extent_size)) {
 164         error_setg(errp, "Extent size %" PRIu32 " is not a power of two",
 165                    s->extent_size);
 166         ret = -EINVAL;
 167         goto fail;
 168     } else if (s->extent_size > 0x800000) {
 169         error_setg(errp, "Extent size %" PRIu32 " is too large",
 170                    s->extent_size);
 171         ret = -EINVAL;
 172         goto fail;
 173     }
 174
 175     if (s->catalog_size < DIV_ROUND_UP(bs->total_sectors,
 176                                        s->extent_size / BDRV_SECTOR_SIZE))
 177     {
 178         error_setg(errp, "Catalog size is too small for this disk size");
 179         ret = -EINVAL;
 180         goto fail;
 181     }
 182
 183     qemu_co_mutex_init(&s->lock);
 184     return 0;
 185
 186 fail:
 187     g_free(s->catalog_bitmap);
 188     return ret;
 189 }
 190
 191 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 192 {
 193     BDRVBochsState *s = bs->opaque;
 194     uint64_t offset = sector_num * 512;
 195     uint64_t extent_index, extent_offset, bitmap_offset;
 196     char bitmap_entry;
 197     int ret;
 198
 199     // seek to sector
 200     extent_index = offset / s->extent_size;
 201     extent_offset = (offset % s->extent_size) / 512;
 202
 203     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 204         return 0; /* not allocated */
 205     }
 206
 207     bitmap_offset = s->data_offset +
 208         (512 * (uint64_t) s->catalog_bitmap[extent_index] *
 209         (s->extent_blocks + s->bitmap_blocks));
 210
 211     /* read in bitmap for current extent */
 212     ret = bdrv_pread(bs->file->bs, bitmap_offset + (extent_offset / 8),
 213                      &bitmap_entry, 1);
 214     if (ret < 0) {
 215         return ret;
 216     }
 217
 218     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 219         return 0; /* not allocated */
 220     }
 221
 222     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 223 }
 224
 225 static int coroutine_fn
 226 bochs_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
 227                 QEMUIOVector *qiov, int flags)
 228 {
 229     BDRVBochsState *s = bs->opaque;
 230     uint64_t sector_num = offset >> BDRV_SECTOR_BITS;
 231     int nb_sectors = bytes >> BDRV_SECTOR_BITS;
 232     uint64_t bytes_done = 0;
 233     QEMUIOVector local_qiov;
 234     int ret;
 235
 236     assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
 237     assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
 238
 239     qemu_iovec_init(&local_qiov, qiov->niov);
 240     qemu_co_mutex_lock(&s->lock);
 241
 242     while (nb_sectors > 0) {
 243         int64_t block_offset = seek_to_sector(bs, sector_num);
 244         if (block_offset < 0) {
 245             ret = block_offset;
 246             goto fail;
 247         }
 248
 249         qemu_iovec_reset(&local_qiov);
 250         qemu_iovec_concat(&local_qiov, qiov, bytes_done, 512);
 251
 252         if (block_offset > 0) {
 253             ret = bdrv_co_preadv(bs->file->bs, block_offset, 512,
 254                                  &local_qiov, 0);
 255             if (ret < 0) {
 256                 goto fail;
 257             }
 258         } else {
 259             qemu_iovec_memset(&local_qiov, 0, 0, 512);
 260         }
 261         nb_sectors--;
 262         sector_num++;
 263         bytes_done += 512;
 264     }
 265
 266     ret = 0;
 267 fail:
 268     qemu_co_mutex_unlock(&s->lock);
 269     qemu_iovec_destroy(&local_qiov);
 270
 271     return ret;
 272 }
 273
 274 static void bochs_close(BlockDriverState *bs)
 275 {
 276     BDRVBochsState *s = bs->opaque;
 277     g_free(s->catalog_bitmap);
 278 }
 279
 280 static BlockDriver bdrv_bochs = {
 281     .format_name        = "bochs",
 282     .instance_size      = sizeof(BDRVBochsState),
 283     .bdrv_probe         = bochs_probe,
 284     .bdrv_open          = bochs_open,
 285     .bdrv_co_preadv = bochs_co_preadv,
 286     .bdrv_close         = bochs_close,
 287 };
 288
 289 static void bdrv_bochs_init(void)
 290 {
 291     bdrv_register(&bdrv_bochs);
 292 }
 293
 294 block_init(bdrv_bochs_init);